【作者】 贺明妍；

【导师】 梁德群；

【作者基本信息】 大连海事大学 ， 通信与信息系统， 2011， 博士

【摘要】 近年来,随着移动通信和因特网的融合,数字通信技术得到了前所未有的发展,人们对通信的多样化和便捷性提出了越来越高的要求。虽然为应对当代社会对通信技术不断提高的要求,各种新技术层出不穷,但调制技术的发展却相对缓慢。其中,正交频分复用技术(OFDM)作为一项多载波调制技术,相对于其他调制方法在数据传输效率上具有明显优势,已被多种通信标准所采用,但实际应用中在某些技术性能上受到了限制,最明显的就是对频率偏移敏感和高的峰值均值功率比。时移非正交多载波调制技术(TS-NMT)是一种具有全新思想的多载波调制技术。TS-NMT与OFDM同属于多载波调制,最大的不同是TS-NMT时域上的每一个子载波的起点有一个离开符号起点的延迟,这个延迟被称为时移,时移进一步造成频域上不同频率的子信道不再正交。这给TS-NMT带来了一系列优秀的特性,同时也带来了信号处理的新问题。我们的前期研究工作已经从理论上证明了非正交调制在传输效率上优于正交调制,并且计算机仿真和物理有线及无线信道的实验也证明TS-NMT比OFDM具有更高的效率和其它优良特性。但单纯的实验验证是不够的,考虑OFDM已经成为当前数字通信中的主流调制技术,有必要从理论上对TS-NMT和OFDM的多种性能做定量的分析对比,这正是本文工作的第一个重点。理论上的定量分析比较,将为TS-NMT替代OFDM走向实用奠定坚实的理论基础。本文另一个重点是根据TS-NMT的优良特性探讨如何将其应用于实际。具体工作包括：(1)对TS-NMT调制和解调过程中的相关问题和解决方案进行了分析和研究,包括子载波间干扰(Inter Sub-Symbol Intefrence, ISSI)和病态性的分析及解决方法。在分析TS-NMT波形结构特点的基础上,总结出TS-NMT具有时域和频域紧性的特点。所谓时域紧性指的是,TS-NMT利用时移特性,将多个单载波的多个符号的波形“挤压”在一个符号中,提高了时域的效率；所谓频域紧性指的是,子信道的非正交性可以让各个子信道更紧密的排列,大大压缩占用带宽。时频域的紧性特点是形成TS-NMT优良特性的基础。从Nyquist提出数字通信的理想系统至今已经80多年,数字通信基本是以在Fourier分析基础上发展起来的正交分析法为主要工具。为了给非正交调制提供更多的理论依据,本论文讨论了用分数频傅立叶级数(FFFS)分解的方法对信号进行合成和分解,实验证明FFFS比传统的正交傅立叶级数(FS)在压缩带宽、逼近项数、与原函数逼近度、Gibbs现象等方面比正交分解具有更好的性能。这也从另一侧面为非正交调制提供了理论支持。(2)对TS-NMT和OFDM的性能进行了理论上的定量分析对比：①利用星座图分析法推导出TS-NMT与OFDM两者单子信道的频谱效率之比ηNS/O的公式及相应曲线,当TS-NMT单子信道的子波数在4-60时,有1<ηNS/O≤5；根据TS-NMT频域紧性的特点,得到ΔfN<Δfo(ΔfN和Δfo分别为TS-NMT与OFDM的子信道频率间隔),从而得出TS-NMT的信号带宽可大大压缩的结论,频谱效率之比加倍提高；②根据TS-NMT的时移特性造成各子波同向相加的概率降低的特点,验证了TS-NMT合成波的最大幅度随子载波数的增长速度远远低于OFDM,从而得出在峰值均值功率比(PAPR)方面TS-NMT比OFDM具有先天优势的结论；③提出将信号由频移造成的误差转换成等效噪声功率的方法,理论和实验结果表明TS-NMT在抗频偏能力上优于OFDM；④在频谱效率分析的基础上,进一步利用星座图分析法证明了TS-NMT的功率消耗小于OFDM.(3)高效利用传感器节点的有限电池能源是无线传感器网络(Wireless Sensor Network,WSN)的关键技术之一。本论文基于对TS-NMT的功耗性能的理论分析及比OFDM低功耗的特点,提出将其应用于无线传感器网络的思想,并在理论推导及同等实验条件下,验证了TS-NMT单位比特功耗低于QPSK,TS-NMT在WSN的节能方面具有一定的应用前景。(4)本文对TS-NMT在VDSL线路进行了应用仿真,搭建了VDSL传输线路的仿真环境——信道模型和噪声模型,将TS-NMT和DMT在同等实验条件下置于VDSL仿真环境中进行实验比较。实验结果表明,TS-NMT在VDSL线路上的传输性能优于DMT(OFDM在VDSL应用中的另一名称)。验证了TS-NMT的实用可行性及优于OFDM的特性。利用TS-NMT的频域紧性的特点,提出一种通过压缩占用带宽将用户分组的方法,减少了self-FEXT串扰,从而达到提高比特传输率的目的。更多还原

【Abstract】 In recent years, digital communication technology has received rapid development with the integration of mobile communications and internet, but the better performance of communication system is still required. Although various new technologies have emerged to meet the requirements, the development of modulation methods is slower. OFDM has obvious advantages in data transmission efficiency as a multi-carrier modulation technique compared with other modulation methods, which has been used in a variety of communication standards. However, the OFDM system has two major drawbacks:high Peak to Average Power Ratio (PAPR) and sensitivity to frequency shift, which limit performances of OFDM.TS-NMT is a novel multi-carrier modulation technology. Both TS-NMT and OFDM are multi-carrier modulation technologies. The main difference between them is that each sub-carrier has a time delay to the starting point of the symbol, which is called Time-Shift. As a result of the Time-Shift, the different frequcncy sub-channels are no longer orthogonal, which provides some excellent performances to TS-NMT and also leads to new signal processing problems. Recent researches have proved that the superiority of TS-NMT to traditional orthogonal methods in transmission efficiency. Computer simulations and physical wired and wirelss experiments have proved that TS-NMT is superior to OFDM in transmission efficiency and other performances. OFDM has become the major modulation technology, so the theoretical and experimental analysis and comparison between TS-NMT and OFDM are necessary. The main contributions are the quantitative analysis and comparison between TS-NMT and OFDM and the applications of TS-NMT. The main work is as follows:(1) The relevant issues and resolutions during modulation and demodulation are analyzed, such as the Inter Sub-Symbol Intefrence (ISSI) and ill-conditionality in the equation group of TS-NMT. Based on the wave structure of TS-NMT, the characteristics of time domain and frequency domain compactness are proposed. Due to the Time-Shif character of TS-NMT, many symbols of the single carrier modulation are compacted into one symbol in time domain. Due to the non-orthogonality character of TS-NMT, sub-channels of TS-NMT are closer in frequency domain to reduce the bandewidth greatly. The non-orthogonal idea has been used in general signal processing. The method of Fourier Series with fractional frequency intervals (FFFS) for the decomposition of signals is proposed, and experiments show that FFFS can provide better performance than FS.(2) The quantitative analysis and comparison between TS-NMT and OFDM are made and listed as follows:①According to the principle of constellation diagram analysis, the formulaηNS.o of the spectrum efficiency ratio of the sub-channel is derived. When the number of the sub-carriers in one sub-channel is 4～60,ηNS o is between one and five. Based on the frequency domain compactness,ΔfN is smaller thanΔfo, whereΔfN andΔfo are the frequency intervals of TS-NMT and OFDM respectively. The bandwidth of TS-NMT could be compressed to improve the spectrum efficiency.②Based on the low probability of adding sub-carriers in the same phase, the maximum amplitude of TS-NMT signal increases slower than the number of sub-carriers. TS-NMT can provide better PAPR than OFDM.③The method of converting the error caused by frequency shift to equivalent noise power is proposed. The theoretical and experimental results prove that TS-NMT has better capability of tolerating frequency shift.④Based on the analysis of spectrum efficiency, it can be proven that, the energy consumption of TS-NMT is less than OFDM according to the constellation diagram analysis.(3) One of the key technologies of WSN is how to improve the efficiency of limited battery power in a single node. Based on the theoretical analysis of energy performance and lower power consumption characteristics of TS-NMT, the idea of applying TS-NMT to WSN is proposed. The theoretical analysis and experiments results prove that TS-NMT is superior to QPSK and the power consumption of one bit is lower. The result proves the practicability of TS-NMT applying to WSN.(4) Finally, computer simulations of TS-NMT in VDSL loop are made. The simulation environment, including the channel model and noise model, is established. The simulation comparison between TS-NMT and DMT is made in the same experimental conditions. Experimental results show that, the transmission performance of TS-NMT is better than DMT in VDSL loop. The result also proves the practicability of TS-NMT. Based on the characteristic of frequency domain compactness of TS-NMT, the users are divided into groups to reduce the self-FEXT noise for high bit rate transmission.更多还原